Question

Consider the following reagents: zinc, copper, mercury (density \(13.6 \mathrm{~g} / \mathrm{mL}\) ), silver nitrate solution, nitric acid solution. (a) Given a \(500-\mathrm{mL}\) Erlenmeyer flask and a balloon, can you combine two or more of the foregoing reagents to initiate a chemical reaction that will inflate the balloon? Write a balanced chemical equation to represent this process. What is the identity of the substance that inflates the balloon? (b) What is the theoretical yield of the substance that fills the balloon? (c) Can you combine two or more of the foregoing reagents to initiate a chemical reaction that will produce metallic silver? Write a balanced chemical equation to represent this process. What ions are left behind in solution? (d) What is the theoretical yield of silver?

Short answer

(a) A suitable chemical reaction that inflates the balloon is the reaction between zinc and nitric acid: \( Zn(s) + 2 HNO_3(aq) \rightarrow Zn(NO_3)_2(aq) + H_2(g) \). The gas that inflates the balloon is hydrogen gas (\(H_2\)). (b) The theoretical yield of hydrogen gas cannot be calculated without more information about the quantities of zinc and nitric acid used in the reaction. (c) A chemical reaction that produces metallic silver is the reaction between copper and silver nitrate: \( Cu(s) + 2 AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2 Ag(s) \). The ions left in the solution are copper nitrate \((Cu^{2+})\) and nitrate ions \((NO_3^{-})\). (d) The theoretical yield of silver cannot be calculated without more information about the quantities of copper and silver nitrate used in the reaction.

Step-by-step solution

(a) Finding a chemical reaction that inflates the balloon

In order to inflate the balloon, we need a chemical reaction that produces a gas. A possible reaction involving the given reagents is the reaction between zinc and nitric acid: \[ Zn(s) + 2 HNO_3(aq) \rightarrow Zn(NO_3)_2(aq) + H_2(g) \] Here, the identity of the gas that inflates the balloon is hydrogen gas (\(H_2\)). This reaction is also balanced, as the number of atoms of each element is the same on both sides of the equation.

(b) Finding the theoretical yield of hydrogen gas

To determine the theoretical yield of hydrogen gas, we need to know the quantities of zinc and nitric acid being used in the reaction. However, the exercise doesn't provide this information, so we cannot calculate the theoretical yield of hydrogen gas without more information about the reagents' quantities.

(c) Finding a chemical reaction that produces metallic silver

A chemical reaction that can produce metallic silver is the reaction between copper metal and silver nitrate solution: \[ Cu(s) + 2 AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2 Ag(s) \] In this reaction, metallic silver (Ag) is produced, and the ions left behind in the solution are copper nitrate \((Cu^{2+})\) and nitrate ions \((NO_3^{-})\). The equation is balanced.

(d) Finding the theoretical yield of silver

Similar to part (b), to determine the theoretical yield of silver, we need to know the quantities of copper and silver nitrate used in the reaction. The exercise does not provide this information, so we cannot calculate the theoretical yield of silver without more information about the reagents' quantities.

Key concepts

Balanced Chemical Equation

A balanced chemical equation represents a chemical reaction where the number of atoms for each element is the same on both the reactant and product sides. This ensures the law of conservation of mass is upheld. When writing a balanced equation, it's crucial to adjust the coefficients (the numbers in front of compounds) rather than altering the subscripts within the chemical formulas. This keeps the integrity of the molecular structure intact.

For instance, in the reaction between zinc and nitric acid to produce hydrogen gas:

• Zinc reacts with nitric acid (\( Zn(s) + 2 HNO_3(aq) \rightarrow Zn(NO_3)_2(aq) + H_2(g) \)).
• Each element on the reactant side has the same count as on the product side.

Ensuring a balanced equation is vital for understanding the stoichiometry and calculating the reactants and products' quantities.

Theoretical Yield

Theoretical yield is the maximum amount of product that can be produced from a given amount of reactants. It's an ideal calculation based on the stoichiometry of the balanced equation, assuming a perfect reaction with no losses.

To determine the theoretical yield, follow these steps:

• Convert all reactants to moles using their molar masses.
• Use the balanced chemical equation to find the mole ratio between the reactant and product.
• Calculate the amount of product in moles and then convert it to grams using the molar mass.

However, in the exercise provided, we're missing the necessary quantities to calculate the theoretical yield for products like hydrogen gas or metallic silver. Therefore, the calculations can't be carried out without additional data.

Hydrogen Gas

Hydrogen gas (\( H_2 \)) is a diatomic molecule and the lightest element in the periodic table. It's commonly produced in chemical reactions involving acids and metals. In the given exercise, the reaction between zinc and nitric acid produces hydrogen gas:

• This gas is what causes the balloon to inflate in the scenario described.
• Hydrogen gas is colorless, odorless, and highly flammable, which means it needs to be handled carefully during experiments.

Understanding how hydrogen gas is produced helps students learn about gas evolution reactions and the principles of chemical reactivity.

Metallic Silver

Metallic silver (\( Ag \)) can be produced through a chemical reaction involving silver nitrate and copper. This illustrates a single-displacement reaction where a more reactive metal (copper) displaces a less reactive metal (silver) from its compound:

• The reaction is written as \( Cu(s) + 2 AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2 Ag(s) \).
• In this process, solid metallic silver is a product, while copper nitrate remains dissolved in the solution.

This type of reaction is significant for understanding reactivity series and for practical applications such as silver recovery and refining processes.